1. Field of the Invention
The instant invention relates generally to fuel injection systems, and more particularly to electronically operated control valves for regulating the quantity of fuel dispensed by each injector within a fuel injection system, and for adjusting the timing of the dispensing in dependence upon various engine parameters.
2. Prior Art
Fuel injectors that are driven mechanically from the crankshaft of an internal combustion engine to deliver fuel into the cylinders of an internal combustion engine are well known; see, for example, U.S. ,at. No. 2,997,994, granted Aug. 29, 1961 to Robert F. Falberg. The movement of the crankshaft is translated into a force that periodically depresses the pump plunger via a cam, cam follower, and rocker arm mechanism. Since the rotation of the crankshaft reflects only engine speed, the frequency of the fuel injection operation was not adjustable with respect to other engine operating conditions. To illustrate, at cranking speeds, at heavy loads, and at maximum speeds, the timing and the metering (quantity) function for the fuel injector did not take into account actual engine operating conditions.
In order to enable adjustments to be made in the timing of the fuel injection phase of the cycle of operation, Falberg proposed that a fluid pressure pump 40 introduce fluid into a follower chamber 37 to elevate a plunger 35 and thus alter the position of push rod 6 which operates plunger member 12 of the fuel injector. By selecting the effective area of the plunger, the elevation thereof advances the plunger member relative to the desired point in the cycle of engine operation. The fluid pressure pump is driven by the internal combustion engine, and a lubricating oil pressure pump is frequently utilized as the fluid pressure pump.
U.S. Pat. No. 3,859,973, granted Jan. 14, 1975 to Alexander Dreisin, discloses a hydraulic timing clyinder 15 that is connected to the lubricating oil system for hydraulically retarding, or advancing, fuel injection for the cranking and the running speeds of an internal combustion engine. The hydraulic timing cylinder is positioned between the cam 3 which is secured to the engine crankshaft and the hydraulic plunger 38. The pressure in the lubrication oil pump 160 is related to the speed of the engine 1, as shown in FIG. 1.
U.S. Pat. No. 3,951,117, granted Apr. 20, 1976 to Julius Perr, discloses a fuel supply system including hydraulic means for automatically adjusting the timing of fuel injection to optimize engine performance. The embodiment of the system shown in FIGS. 1-4 comprises an injection pump 17 including a body 151 having a charge chamber 153 and a timing chamber 154 formed therein. The charge chamber is connected to receive fuel from a first variable pressure fuel supply (such as valve 42, passage 44, and line 182), and the timing chamber is connected to receive fuel from a second variable pressure fuel supply over line 231, while being influenced by pressure modifying devices 222 and 223. The body further includes a passage 191 that leads through a distributor 187 which delivers the fuel sequentially to each injector 15 within a set of injectors.
A timing piston 156 is reciprocably mounted in the body of the injection pump in Perr between the charge and timing chambers, and a plunger 163 is reciprocably mounted in the body for exerting pressure on fuel in the timing chamber. The fuel in the timing chamber forms a hydraulic link between the plunger and the timing piston, and the length of the link may be varied by controlling the quantity of fuel metered into the timing chamber. The quantity of fuel is a function of the pressure of the fuel supplied thereto, the pressure, in turn, being responsive to certain engine operating parameters, such as speed and load. Movement of the plunger 163 in an injection stroke results in movement of the hydraulic link and the timing piston, thereby forcing fuel into the selected combustion chamber. The fuel in the timing chamber is spilled, or vented, at the end of each injection stroke into spill port 177 and spill passage 176. The mechanically driven fuel injector, per se, is shown in FIGS. 14-17.
All of the above-described fuel injection systems employ hydraulic adjustment means to alter the timing of the injection phase of the cycle of operation of a set of injectors mechanically driven from the crankshaft of an internal combustion engine, and the hydraulic means may be responsive to the speed of the engine and/or the load imposed thereon. While the prior art systems functioned satisfactorily in most instances, several operational deficiences were noted. For example, the hydraulic adjustment means functioned effectively over a relatively narrow range of speeds, and responded rather slowly to changes in the operating parameters of the engine. Also, problems were encountered in sealing the hydraulic adjustment means, for a rotor-distributor pump was utilized to deliver hydraulic fluid to each of the fuel injectors in the set employed within the fuel injection system. In order to provide a hydraulic adjustment means responsive to both speed and/or the load factor, as suggested in the Perr patent, an intricate, multi-component assembly is required, thus leading to high production costs, difficulty in installation and maintenance, and reduced reliability in performance.
The deficiencies of the known fuel injection systems utilizing hydraulic adjustment means to control fuel injection prompted the applicants and other research personnel in the laboratories of the corporate assignee to investigate and develop an electronically operated fuel injector assembly, either an assembly employing one injector for each cylinder of the engine, or a common rail system.